CVE-2026-26021 Prototype pollution in set-in
Prototype pollution in set-in allows attackers to modify Object.prototype via crafted input, potentially leading to code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-26021?
CVE-2026-26021 is a critical code injection vulnerability in ahdinosaur set-in, published on 11 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
set-in provides the set value of nested associative structure given array of keys. A prototype pollution vulnerability exists in the the npm package set-in (>=2.0.1, < 2.0.5). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. This has been fixed in version 2.0.5.
Weakness: CWE-1321
Which versions are affected by CVE-2026-26021?
2 open source packages ship an affected version, including set-in. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
set-in npm | From 2.0.1 | 2.0.5 |
set-in npm | From 2.0.1 | 2.0.5 |
Products include Set-in Project Set-In.
How do I fix CVE-2026-26021?
Upgrade set-in to 2.0.5 or later.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-26021 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-26021 exists.
Other vulnerabilities in ahdinosaur set-in
Sources
Also known as GHSA-2c4m-g7rx-63q7.